Apparatus for the roasting of pellets



1964 K. MEYER ETAL 3,

APPARATUS FOR THE ROASTING OF PELLETS Filed March 29, 1965 6 Sheets-Sheet i F ig. 1

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Dec. 8, 1964 K. MEYER ETAL 3,160,402

APPARATUS FOR THE ROASTING 0F PELLETS Filed March 29, 1963 6 Sheets-Sheet 2 .7nrenlars:

Dec. 8, 1964 K. MEYER ETAL 3,160,402

APPARATUS FOR THE ROASTING 0F PELLETS Filed March 29, 1963 6 Sheets-Sheet 3 I I & 3 a

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Siam c United States Patent 6 3,160,402 APPARATUS FDR THE ROASTZNG F PELLETS Kurt Meyer and Georg von Struve, Frankfurt am Main,

Germany, assignors to Metaligeselischaft Alrtiengesellschaft, Frankfurt am Main, Germany Filed Mar. 29, 1963, Ser. No. 268,8?5

Claims pricrity, application Germany, Apr. ill, 1962,

M 52,462; Aug. 3, 1962, M 53,782; Sept. 7, H62,

18 Claims. (til. Zea-as This invention relates to the roasting, rying or the like of pellets made from ore, raw materials for making cement, or any other material needing similar treatment, or the sintering of finer grained ores or the like, all upon a circular rotatable grate.

Treating green pellets on a linearly moving grate is conventional. In such, the fullest advantage is gained only when the bed of green pellets formed on the grate has av uniform thickness or depth. It is not dimcult to obtain a uniform bed on a linearly moving grate. It is only necessary to be sure that the green pellet feeding mechanism discharges a uniform stream of pellets across the entire width of the grate while the grate is advancing evenly beneath the feeding mechanism.

However, when using rotating circular grates for the sintering of ores and the like, the conventional feeding mechanism will not produce a uniformly thick bed on the grate because, even though the speed of rotation of the grate is constant, the circumferential velocity of the various circular parts of the grate increases with the increase of the radius of the circular part. This disadvan tage is easily correctable when sintering unpelleted finegrained material because the surface of the bed is smoothed out by suitable simple devices, such as scrapers. However, when the bed is composed of pellets, such scrapers cannot be used because they crush a large quantity of the green pellets and thus nullify the pelletizing. Apparently this is one of the reasons why pellets are ordinarily roasted only on linearly moving grates. In practice, a circular rotating grate has not been used extensively even for the sintering of unpelleted fine-grained materials. This is explained to some extent because, as a rule, the end product was unevenly roasted which resulted in too much unusable residual material. This disadvantage is even of greater significance with respect to the heat hardening of green pellets than it is with the roasting of unpelletized fine-grained material since the pelletizing step produces relatively more expensive green pellets, and the re-pelletizing of a large portion of the crushed residual material means a very uneconomical use of a rotating circular grate.

According to this invention, it has been surprisingly found that the economy in operating a rotating circular grate depends to agreat extent upon the manner in which the materials to be treated are fed to the grate to form the bed. Heretofore, these materials were introduced to the grate through high hopper having a relatively wide bottom discharge opening extending across the en a tire width of the circular grate. The trailing edge of this bottom opening as viewed in the direction of rotation of the grate is at the level of the surface of the bed being formed on the grate.

and furthermore, varies greatly between those of equally high values and those that are twice as high. The reason for this possibly lies in that with an even grate rotating speed, the circumferential velocities of the circular portions of the grate rise as the radius increases from the center of rotation of the grate and the quantity of material discharged from the hopper decreases proportionally, it being noted, however, that the material flows out very irregularly from the hopper. The pressure differences that thus arise cause, in turn, a varying thickness in the bed formed on the grate which results in a variable permeability in the bed to the passage of the 'hot gases drawn through the bed for the roasting or sintering of the pellets. Thus this further contributes to the uneven roasting of sintering of the pellets and the resulting high percentage of unusable sintered material.

In this invention, early experiments to adapt conventional feeding devices to a rotating circular grate in order to eliminate the pressure of the weight of the material being discharged upon the bed partially formed on the grate were unsuccessful. For example, the Weight of the material being fed to the bed on' the grate was held by bafiles so that the material reached the bed in free A fall. Again, the material was fed to the grate by a conveyor belt running parallel to the surface of the grate. In each of'these cases, it was. necessary to smooth the surface of the bed of pellets formed on the grate by means of scrapers, because an uneven bed surface was formed by the various velocities of the circular portions of the grate. Even so, as great quantities of material are being handled, the bed of pellets always was of uneven thickness. Again a large portion of the green pellets were crushed and destroyed when fed to the grate.

An object of this invention is to economically use a rotating circular grate for the roasting or pelletizing of fine-grained material, cenient raw material or the like; Another object of this invention is to produce a means by which a circular rotating grate can be charged with a bed of raw material, which bed has a level surface across the entire width of the grate and is of even thickness there-.

through, so that a uniformly treated product is obtained and with but an insignificantly small amount of unusable residual material. A further object of the invention is to produce a means for forming a bed on the grate composed of undamaged green pellets, which bed is of uniform thickness throughout. Other objects and advantages of the invention are hereafter set forth. p

In general, the objects of the invention are obtained first by using a pellet feeding mechanism which uniformly distributes the raw material across the entire width of the grate of a rotating circular roasting or sintering appa-. ratus. ,The dumping points'of the feeding mechanism have discharge capacities with'respect to one another as their radial distance from the center of rotation of the grate are related to one another. Accordingly, the affect of the diderent circumferential speeds of the diiferent portions of the grate are'equalized with the result that a substantially completely even bed thickness is formed across the entire width of the moving grate.

The uneven thickness of the bed of pellets formed on the grate and the crushing of the green pellets is further avoided by the provision of means for'conveying the green pellets to the dumping points at an-angle of not more than 45 to the horizontal, preferably at angles of 0 to 20, and by positioning the dumping points not much higher above the surface of the travelling'grate than'the height that the charge upon said grate should assume.

The dumping points are composed ofslots, dumping edges and the like which extend approximately'inthe direction of rotation of the circular grate. In this case their length is chosen so that the individual len'gths of b the dumping slots or edges are related to one another as their respective radial distances from the center turning point of the circular grate. By positioning these dumping slots and/or edges parallel to the rotational di rection of the grate, the dissimilarities in the bed caused by the different circumferential velocities of the individual circular portions of the grate are completely eliminated. Up to a certain degree and mostly in a very satisfactory manner this is alsotrue when the dumping slots and/or edges diverge from the direction of rotation of the grate. -However, this diversion must not amount to 90, since otherwise the'evening effect of the various lengths of the'dumping edges is completely nullified. The diversion should not be large as a" narrow angle of diversion produces in many cases an even bed surface. A large diversion will cause a too great a variation in the thickness of the bed. I

r The feeding mechanism in one form of the invention is composed of conveyor belts which move the green pellet-s either radially inward or outward to the circular; rotating grate. These belts terminate at different dumping points above the grate, which points are uniformly distributed across the Width of the grateyso that the grate is charged with pellets across its entire width. The width of the individual belts, or ratherthe widths of theirdumping edges are related to each other as their distance from the center of rotation of the grate. The

individual belts are placed either in the same plane or in different planes with respect to each other. 7 I

The amount of material discharged from the belts onto the circular grate according to another feature of the invention is controlled at the respective dumping points of the belt by using belts of equal width and giving each belt a speed proportional to the velocity of the circular portion of the grate lying at the dumping edge for that belt.

As in linearly moving grates, it is also advantageous in a circular rotating grate to provide a grate protective layer composed of inert materials, side wall protective layers, and often a protective cover layer. The feeding mechanism of this invention is combined with additional feeding mechanism for forming these protective layers.

In a further form of the invention, the feeding mechanism for the circular grate is composed of one or several roller conveyors. The term roller conveyor describes an apparatus composed of a series of horizontal parallel rollers driven to rotate in the same direction toward the slots canbe curved and each curve has a radius which corresponds to its radial distance to the'center of rotation of the-grate; By so doing, it is assured that the quantity of material discharged onto the grate at all points is proportional to the rotational velocity of the grate to'ensure an absolutely uniform depth of the bed of material formed on the grate. The hopper and/0r hoppers may be sub-divided, which is especially expedient for a hopper used to form the protective grate layer and the side wall protecting layers. The hopper in this case has three divisions. The middle portion holds the grate protective layer material "and the end divisions hold the side wall protecting material. It is best to keep the hopper for thegreen pellets in low as possible and I to keep it filled sumciently to a height which does not substantially exceed the height of the bed being formed on the grate, and this is done by constantly feeding the hopper by means of conveyor belts or roller conveyors dumping point.- The sizes of the individual green pellets being conveyed by the rollers are large enough in order to move the individual pellets out of the valleysbetween of rotation of the grate.

Several roller conveyors can be used as, for example,

a first roller conveyor is used to form the bed of green pellets and a second roller conveyoris. used to form;

the protective grate layer-and. the side wall protecting layers. In this case, the material is conveyed toward the outer circumference of the grate as well as from the center of rotation of the circular grate; Also, the

. or the like.

'of the pellets.

This ensures an especially careful handling It has been found that by using the above-described pellet feeding means, asubstantially uniform thickness of the bed on the rotating circular grate is indeed obtained. However, because of the sharply defined limits alleviated by positioning'the dumpingledges diagonal or somewhat inclined to the direction of rotation of the grate, but it is not completely avoided. Moreover, these described feeding meanshave relatively little flexibility with'regard' to the fixing of the surface of the pellet bed across the various widths of the grate.

According to this invention, one improvement in this regard is the provision of means for feeding the pellets onto the circular grate in which the dumping points merge into one another across the width of the grate, and in which control devices are used to distribute the quantities of pellets to the dumping points in proportion to theradialdistance of the same fromthe center of rotation of the grate. j 7

Thus in one form of this invention, roller conveyors with rollers of uniforrn length are arranged above the circular" grate so that the material discharge or dumping roller extends longitudinally approximately radially across I the width of the grate. Material directing adjustable baflies' are positioned above and'along the width of the conveyor in order to distrihute'the stream of pellets flowing over the dumping edges of the conveyor at rates cornrnens'urate with the distance of the dumping edges fromthe center of rotation of the grate. These baffles pref erably are mounted so that they can be horizontally displacedwith respect to the conveyor dumping edges. This not only allowsthe adjusting of the dumping capacity of the grate as being directly proportional to the distance of the dumping points from the center of rotationof the grate, but also'permits the formation of a uniform surface on the bed ofpellets, t V

to the distributionof the The same effect with regard vmaterial on the grate is achieved with a roller conveyor composed .of even length rollers having a longitudinal dumping edge positioned radially ofthe grate and mount ed above the grate pivotally adjacent the outer circun1- ference of the grate and further pivotally mounted addumping edgesof the'rollers can extend in the direction of the rotation of thegrate as well as counter thereto- In another modified form of the invention, one or several-feeding hoppers are used, whose bottoms are slotted to provide openings distributedover the entire width of the grate and further extending longitudinally in the di-' rectionuojf rotation of.t he grate. Here again, the lengths of the slots are-relatedt'o each other asare their radial.

jacent the'edge'of the discharge roller'so that the dumpa ing edge'of. the conveyor is displaceable in twodirections at right anglesto each otheri or in other Words, the grate can be simultaneously'tilted in two directions, This has the advantage in that the pellets are carefully handled and the directional baffles which'are subject to rapid wear and tear areo'rnitted. However, baflles can be used for this displaceable roller conveyor when a flexible distribution of the stream of pelletsis desired. In such case, fewer baffles .are'necessary than with anon-pivoting conveyor.

Accordinglto another modification of this invention wherein-'thevoiume of flow of the pellets is dependent j 3 upon the radial distance between the dumping points and the center of rotation and the grate is in that the roller conveyor is supplied with pellets coming from a forwardly and backwardly moving conveyor belt whose dumping edge moves across the entire width of the roller conveyor with an increasing or decreasing velocity that is proportional to the radial distance between the dumping point of the conveyor and the center of rotation of the grate. For finely adjusting the volume of material dumped from the dumping points of the roller conveyor from which the material goes directly into the grate, the roller conveyor isdisplaceable additionally around the dumping or discharge edges, and/ or may be provided with material directing baflles as heretofore described.

In order to produce a completely smooth surface on the bed of pellets in the grate, and especially when, because of operationalor economic reasons, the abovedescribed fine adjustment can be used only to a limited extent, this invention contemplates the mounting of a hopper in addition to that for the green pellets and following the green pellet hopper for adding a surface layer of already roasted or inert pellets or the like on top of the bed of green pellets. This additional hopper has a very small discharge slot. Its trailing edge, as seen in the direction of the rotation of the grate, regulates the thickness of this cover layer of roasted pellets with respect to the distance of the edge from the surface of the bed of green pellets. Furthermore, this edge functions as a spreading knife to produce a smoothing and spreading effect. If necessary, an additional spreading knife is provided. It has been discovered that the green pellets lying beneath this cover layer of roasting pellets are not damaged by this technique. Even the density of the green pellet bed is not adversely changed by this cover layer probably only because relatively small amounts of material are moved and the weight of the column of roasted pellets within the additional hopper is mostly supported by the walls of the hopper because of the relatively narrow discharge slot in the bottom of the hopper. Also, when using dry and smoothly flowing roasted pellets, the slots do not get stopped up as easily as occurs with finegrained and moist material.

The means by which these and other objects of the invention are obtained are described more fully with reference to the accompanying drawings, in which:

FIGURE 1 is a partial plan view of a circular rotating grate and a roller conveyor, the rollers of which have dumping edges of difierent lengths;

FIGURE 2 is a plan view of a modification of FIGURE 1 in which each roller has two dumping edges;-

FIGURE 3 is a further modification of FIGURE 1 in which a plurality of different widthconveyor belts are directed generally toward the center of rotation of the circular grate;

FIGURE 4 is a further modification of FIGURE 1 in which conveyor belts of equal width extend both toward the center of rotation of the grate and tangentially of respective circular portions of the grate;

FIGURE 5 is a view similar to FIGURE 1 of a further modification in which a roller conveyor ofeven length rollers extends generally tangentially of the grate and with material directing batlies for directing the material to the dumping edge of the conveyor in amounts dependent upon the respective dumping points of the center ofrotation of the grate; I

FIGURE 6 is an enlarged 'detailed view of the baflie holding means shown in FIGURE 5; I

FIGURE 7 is a schematic perspective "view of a fur ther modification of the invention'-; in which the roller conveyor extends generally tangentially. to the grate and is pivotally mounted for swinging on two side edges; and FIGURE 8 is a view similar to FIGURE 1 of a further modification of the invention in which conveyor belts feed material'into a hopper having a plurality of bottom the grate with each belt having a speed related to the openings forming discharge slots and each of which has a length proportional to the radial distance of the slot from the center of rotation of the grate.

As shown in FIGURE 1, a circular rotating grate of known construction is provided with a ring gear 2 so that it is turned around the axis of rotation 3 by means of gear 4 at a uniform speed and in the direction shown by arrow A. A roller conveyor 5 extends generally toward the center of rotaton of the grate and is composed of a plurality of rollers for the purpose of transporting material, such as green pellets made from fine-grained ores, cement raw materials, and the like. This roller conveyor 5 is novel in that it is composed of a plurality of rollers 6 of different longitudinal lengths. Consequently, above the grate, the conveyor has different length dumping edges 7, 8, 9, 1G, 11 and 12. The rollers are all driven at the same speed by means of chain 13. The lengths of the dumping edges are related to each other in proportion to the circumference of the circular portions of the grate lying beneath each dumping edge. This proportion is the same as that between the lengths of the edges and the radial distance between the edges and the center of rotationof the grate. Conveyor 5 is positioned above the grate so that the dumping edges 7 to 12 are only slightly above the surface of the bed of material being formed on the grate, such as green ore pellets or cement raw materials or the like. As known to the art, the thickness of the bed is regulated by controlling the relation between the relatively low rotational speed of the grate to the conveying speed of the roller conveyor. According to this invention, the uniformity of thickness of the bed over the width of the grate is obtained simply by means of the different length dumping edges of the roller conveyor. At the same time, the green pellets are gently handled and a bed of uniform density is built up.

In the modification of FIGURE 2, the roller conveyor 5 also extends generally toward the center of rotation of v the gate, but the rollers are centrally aligned so as to have the dumping edges 7 to 12 and, in addition, to have dumping edges 14, 15, 16, 17, 18 and 19. This-arrangement, and with the use of material directing baffies 20, 21 and 22, a roller conveyor of this type can simultaneously discharge into the grate the grate protective layer ofinert material and the side wall protecting layers of inert material.

In the modification of FIGURE 3, parallel conveyor belts 23, 24, 25, 26 and 27 are of different widths and extend generally toward the center of rotation of the grate. These belts are all driven at the same speed by chain 13 and common drive shaft 28. According to the principle of this invention, the width of each belt is proportional to the distance of its dumping edge to the center of rotation of the grate and/or to the circular portions of'the grate beneath the dumping edges, respectively. This modificationachieves the same material delivery to the grate as described for the roller conveyors of FIGURES 1 and 2. However, as contrasted toroller conveyors, this modification can deliver fine-grained raw materials rather erally toward the centerof rotation of the grate and the, a other belts extend generally tangentially of the circular portions of the grateQEach belt is driven by an electric motor 30 at a speed proportional to the radial distance between the dumping edge of the belt and the center of rotation of the grate and/ or the circumference of the circular portions of the grate beneath its respective belt dumping edge. The same object, namely asubstantially uniform thickness of the bed on the grate, is also obtained 7 when all the belts feed material radially of the grate or: when'they feed the material tangentially to the grate.

The belts are given pre-determined speeds by conventional driving means. This form of the invention has the adamnesia of discharge roller 61 by means of adjustable material directing bafiles 62. These battles 62 are turnably supported in fittings 63 as shown in FIGURE 6, and these fittings are movably mounted in rails 64. Because these 7 rails ti lextend substantially across the entire Width of conveyor 60, the balfies 6 2 are movable over this distance.

Rails 64 are adjustably supported in fittings 65 by means,

of posts 66'and held in position by a set screw 67. The supports 65 are, in turn, movably mounted on a rail 63 which is positioned along'the side edge of roller conveyor 69.

64). Consequently, it is possible to direct the flow of pellets being transferred by conveyor 69 over the dumping edge of roller 61 in such a manner that the amount of material discharged over each dumping point of the dumping edge of roller 61 is'somewhat merged with the material dumped over the usual'dumping point while the quantity of material falling from each dumping point is proportional to the radius between "that dumping point and the center'of rotation of the grate. A bed of uniform In this modification, the material directing bafiles 62 can be moved into any desired position above conveyor depth is therefor formed across the entire width of grate 1.

Furthermore, in FIGURES, the roller conveyor 6% is followed by a hopper 63 as seen in the, direction ofrotation given by arrow A. Hopper 6h has a relatively narrow' bottom discharge slot 70 which extends entirely across the width of grate 1. This slot increases in width relative to the distance between the dumping points of the slot and the center of rotation of the grate, and therefore widens radially outwardly; Hopper 7t is'us'ed to spread a covery layer of pre-roasted pellets onto the surface of the bed of green pellets formed on grate l and in order to smooth away irregularities which may be present' in the surface of the bed of green pellets. This hopper 70cm be used for all the forms of the invention disclosed herein. 7 V

In FIGURE 7, the roller conveyor 6t) iscomposed of a plurality of even length rollers 61 held by a frame 71. The connections betwee'nthe rollers and the frame and the drive for the rollers are conventional and not shown.

' The rollers are driven so that they feed material in the directionof the arrow A while the grate it rotates" in the same direction. Frame 71 is joined to a lower frame 72 by means-of a hinge 73 which extends'transversely across the width of the grate} so thatthe rollenconveyor can be tilted in the direction of rotationof the grate approxi the thickness of the bed of material to be formed on the grate, which thickness ordinarily is about 50 cm. Hopper 77 has a Wide bottom surface 78 provided with openings forming bottom discharge slots 77. These slots are curved to conform with the curvature of the circular portions of the grate lying beneath them. The lengths of the slots are related to each other as are the distance of the slots from the center of rotation of the grate, and/ or the circumferences of the circularportions of the grate beneath the slots. Belts 51 are driven at different speeds related to each other as the distances between their dumping edges and the center of rotation of the grate in order to maintain a uniform "depth of green pellets within the hopper. However, hopper 77 can also be fed with pellets with the feeding mechanisms shown in FIGURES 3 to 7, inclusive. The quantity of green pellets within the hopper is kept low enough so that the pellets are not damaged or crushed and do not cake together. 'This volume, in

general, is kept not much higher than the intended height of the bed being formed on grate 3i. The advantage of using hopper '77 is in thata pellet bed is formed on grate 1 which is as uniform as possible.

' According to thisinven'tion, the use of the feeding mechanisms described With-a circular rotating sintering apparatus makes it possible for the first time to :operate the sintering apparatus for the roasting of pellets in an economically justified manner and with the obtaining of a roasted product which is technically acceptable. With regard to the quantity of pellets roasted per unit of grate surface, the capacity of the circular sintering apparatus is almost doubled over that obtainable by a linear sinter band. This is because the idle movement of the total grate surface, such as'occurs with the-returning of the pans on the lowerreach of the linear sinter band, is omitted in the circular sinter band. In addition, the circular sinter'band requires less space and especially less structural height andaflords an extraordinarily high investment savings,

Having now describedthemeans .by which the objects of the invention are obtained,'we claim:

. the like, or the sintering of fine grained ores or the like, upon a circular rotating grate, theimprovement comprising conveyor means mounted above said grate for charging material onto said grate, said. conveyor-means including movable conveying surface transporting means for carrying the material in {the direction toward said grate I and-having a discharge edge formed by the reversal of the direction of motion of the surface transporting means by rotation about horizontal axisand at a plurality. of adjacent stationary/dumping points spaced across the width mately about the axis or" the dumping roller 6101 an axis parallel thereto. Lower frame 72 is alsojoined to a support 73a by means of a hinge 74 so that this frame, while carrying frame 71"and'conveyorf6tl, can be tilted transversely of the width ofgrate ton an axis lying outwardly of the grate, Furthermore, frame "lit-when in horizontal position is supported by the horizontal beam 75 joined to by the conveyorbelt 51, shown in FIGURE 5. By simulcomposed offine'graine'dores, raw cement materials and.

of said'grate to dump thematerial in quantities at a rate directly proportional to the distance between each dumping point and the centerof rotation of said grate, respectively directly proportional'to the circle of said grateat adumping point. v

2. Ina'n apparatus 'for the heat'hardening of pellets a the like, or thesintering of finer grained ores or the like,

taneously swinging conveyor dtl'f on. hinges '73 and 74,

it is possible to tilt'conveyor 6t} solthatpellets are dumped from roller 61 in accordance with the principlebf this invention. 'lhedistribution of the pellets along the dumping edge of roller 61- canbe refined by also using the material directing baffles 62 shown inFlGURE ,5. The

supporting means for these baifies are in this case mounted on frame 71 so thatthe'position ofthe baffles relative to the roller conveyor is not altered by the tilting of the conveyor 60.

lnthe modification of FIGURE 8, '5' horizontal hopper 77 is mounted beneath the dumping edges of the belts 51.

upon a circular rotating grate, the improvementfc'omprising conveyor means mounted above said grate forcharga ing material ontosaid grate, said conveyormeans including movable conveying, surface transporting means for carrying the. materialiin the direction toward said grate V and having a discharge edge formed by'the reversal'of the about a horizontal-axis and'being inclined at anlangle of direction of 'the surface transporting means by rotation riotmore than45 to: the surf ac'e ofsaid grateforic affy' ing the materl-ialto a filurality of adjacent dumping points spaced across thef width of 'saidgrateat a rate to dump the mater'ial inin ediatelyas it reaches the dumping points i iaquantitiesdireetlyproportional'to the distance between eachfdumpingfpointand the center of rotation-of said rate.

3. In an apparatus for the heat hardening of pellets composed of fine grained ores, raw cement materials and the like, or the sintering of fine grained ores or the like, upon a circular rotating grate, the improvement com rising conveyor means mounted above said grate for charging material onto said grate, said conveyor means including movable conveying surface transporting means for carrying the material in the direction toward said grate and having a discharge edge formed by the reversal of the direction of the surface transporting means by rotation about a horizontal axis and being inclined at an angle of not more than 29 to the surface of said grate for carrying the material to a plurality of adjacent dumping points spaced across the width of said grate at a rate to dump the material immediately as it reaches the dumping points in quantities directly proportional to the distance between each dumping point and the center of rotation of said grate.

4. In an apparatus for the heat hardening of pellets composed of'fine grained ores, raw cement materials and the like, or the sintering of line grained ores or the like, upon a circular rotating grate, the improvement comprising conveyor means mounted above said grate for charging material onto said grate, said conveyor means including movable conveying surface transporting means for carrying the material in the direction toward said grate and having a discharge edge formed by the reversal of the direction of the surface transporting means by rotation about a horizontal axis and being substantially parallel to the surface of said grate for carrying the material to a plurality of adjacent dum ing points spaced across the width of said grate at a rate to dump the material immediately as it reaches the dumping points in quantities directly proportional to the distance between each dumping point and the center of rotation of said grate.

5. In an apparatus for the heat hardening of pellets composed of line grained ores, raw cement materials and the like, or the sintering of fine grained ores or the like, upon a circular rotating grate, the improvement comprising conveyor means mounted above said grate for charging material onto said grate, said conveyor means including movable conveying surface transporting means for carrying the material in the direction toward said grate and having a discharge edge formed by the reversal of the direction of the surface transporting means by rotation about a horizontal axis and being inclined at an angle of from between about 20 to 45 to the surface of said grate for carrying the material to a plurality of adjacent dumping points spaced across the width of said grate, said points being substantially no higher than the upper surface of the bed of pellets being formed on said grate, and at a rate to dump the material immediately as it reaches the dumping points in quantities directly proportional to the distance between each dumping point and the center of rotation of said grate.

6. In an apparatus as in claim 1, said transporting means comprising a plurality of elements extending substantially tangential to the direction of rotation of said grate, and each element having a material discharge edge with a length corresponding to its distance of that dumping point to the center of rotation of said grate.

7. In an apparatus as in claim 6, said elements comprising a plurality of conveyor belts of different widths extending generally toward'the center of rotation of said grate, and means for driving said belts at the same speed.

8. In an apparatus as in claim 1, said transporting means comprising at least one roller conveyor extending generally'toward the center of rotation of said grate, and the rollers of said roller conveyor decreasing in length toward said center of rotation in proportion to their distance from said center of rotation.

9. In an apparatus as in claim 1, said transporting means comprising a plurality of equal width conveyor belts, and means for driving each belt independently at a speed proportional to the distance between the dumping point of said belt and the center of rotation of said grate.

10. In an apparatus as in claim 1, said transporting means comprising a conveyor inclined to'the horizontal at an angle of less than 45 and having a dumping point edge extending entirely across said grate and generally toward the center of said grate, and means for discharging material from said conveyor along the length of said edge in amounts related to each other as are the distances from the dumping points on said edge to the center of rotation of said grate.

11. In an apparatus as in claim 10, said conveyor comprising a plurality of uniform length rollers extending across and generally toward the center of said grate, and dumping means for discharging material from said rollers onto said grate at dumping points in amounts dependent upon the distance between the respective dumping points and the center of rotation of said grate.

12. In an apparatus as in claim 11, said dumping means comprising frame means holding said rollers and pivotally mounted for inclining said rollers both trans- I versely of said grate and in the direction of rotation of said grate.

13. In an apparatus as in claim 11, said dumping means. 7

including belt means movable relative to said rollers for placing material .on said rollers at pointsi-n amounts relative to the distance between each point and'the center of rotation of said grate.

14. In an apparatus as in claim 12, said frame means being hinged both on an axis transverse to said grate and tangential to said grate.

15. In an apparatus as in claim 1, said transporting means comprising at least one conveyor belt, a hopper for receiving material from said belt and discharging material onto said grate, said hopper having a plurality of bottom openings each of which extends parallel to the circum ference of said grate, and each of which has a length proportional to its radial distance from the center of rotation of said grate.

16. In an apparatus as in claim 15, further comprising means for moving said belt relative to said hopper for placing material in said hopper at said openings in amounts relative to the distance between each opening and the center of rotation of said grate.

17. In an apparatus as in claim 1, further comprising hopper means for forming a cover layer of material on top of the bed of material deposited on said grate by said transporting means.

18. In an apparatus as in claim 10, said means for discharging material from said conveyor including material directing bafie means adjustably mounted above said con- 1 CHARLES SUKALO, Primary Examiner. 7

JOHN J. CAMBY, Examiner. 

1. IN AN APPARATUS FOR THE HEAT HARDENING OF PELLETS COMPOSED OF FINE GRAINED ORES, RAW CEMENT MATERIALS AND THE LIKE, OR THE SINTERING OF FINE GRAINED ORES OR THE LIKE, UPON A CIRCULAR ROTATING GRATE, THE IMPROVEMENT COMPRISING CONVEYOR MEANS MOUNTED ABOVE SAID GRATE FOR CHARGING MATERIAL ONTO SAID GRATE, SAID CONVEYOR MEANS INCLUDING MOVABLE CONVEYING SURFACE TRANSPORTING MEANS FOR CARRYING THE MATERIAL IN THE DIRECTION TOWARD SAID GRATE AND HAVING A DISCHARGE EDGE FORMED BY THE REVERSAL OF THE DIRECTION OF MOTION OF THE SURFACE TRANSPORTING MEANS BY ROTATION ABOUT A HORIZONTAL AXIS AND AT A PLURALITY OF ADJACENT STATIONARY DUMPING POINTS SPACED ACROSS THE WIDTH OF SAID GRATE TO DUMP THE MATERIAL IN QUANTITIES AT A RATE DIRECTLY PROPORTIONAL TO THE DISTANCE BETWEEN EACH DUMPING POINT AND THE CENTER OF ROTATION OF SAID GRATE, RESPEC- 